Phase transitions and ordering structures of a model of chiral helimagnet in three dimensions

TL;DR

This study investigates phase transitions and ordering in a 3D chiral helimagnet model with Dzyaloshinskii--Moriya interaction using advanced Monte Carlo simulations, revealing continuous transitions and critical phenomena.

Contribution

It introduces large-scale Monte Carlo simulations of a 3D chiral helimagnet model, identifying critical behavior and phase structures under magnetic fields.

Findings

Continuous phase transition with 3D XY critical exponents

Emergence of uniaxial helical structure at low temperatures

Existence of a critical point with diverging specific heat and susceptibility

Abstract

Phase transitions in a classical Heisenberg spin model of a chiral helimagnet with the Dzyaloshinskii--Moriya (DM) interaction in three dimensions are numerically studied. By using the event-chain Monte Carlo algorithm recently developed for particle and continuous spin systems, we perform equilibrium Monte Carlo simulations for large systems up to about $10^6$ spins. Without magnetic fields, the system undergoes a continuous phase transition with critical exponents of the three-dimensional \textit{XY} model, and a uniaxial periodic helical structure emerges in the low temperature region. In the presence of a magnetic field perpendicular to the axis of the helical structure, it is found that there exists a critical point on the temperature and magnetic-field phase diagram and that above the critical point the system exhibits a phase transition with strong divergence of the specific heat and the uniform magnetic susceptibility.